Organic semiconductor materials are divided into hole and electron transport materials. These are required, for example, for the manufacture of so-called organic electronic components, such as organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), organic solar cells, generally organic photo-voltaic elements, electrochromatic organic components, organic magnetic sensors, organic memory elements and/or organic photodetectors.
In the case of the hole transport materials, very efficient and stable structures have been developed in the last 15 years, which, according to the application, are available with a wide variety of different hole injection properties and form stable free-radical cations in the hole-transporting, oxidized state.
In the case of the electron transport materials, there are to date only very few representatives of this material property, both in terms of the range of electron injection and in terms of the stability of these materials in the electron-transporting, reducing state, and so, more particularly, the free-radical anions cannot be formed reversibly over a prolonged period.
Good electron conductors are considered at the present time to be the derivatives of phenanthroline (BCP and BPhen) and derivatives of oxadiazole. The free-radical anionic species which are formed during the operation of these components lead to a change in geometry in the heterocyclic structures, such that the electron trans-port propensity decreases as a consequence of the formation of interrupted conjugation.